The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Generally, a microphone, which converts a voice into an electrical signal, may be applied to various devices such as a mobile communication device, an earphone, a hearing aid, etc.
The microphone has been downsized, and microelectromechanical system (MEMS) microphones are being developed based on a microelectromechanical system (MEMS) technology.
Such an MEMS microphone may be manufactured by a semiconductor batch process. It may have a stronger humidity resistance and heat resistance than a conventional electret condenser microphone (ECM). Also, its size may become smaller and it may be integrated with a signal processing circuit.
The MEMS microphone may be classified into a piezoelectric MEMS microphone and a capacitive MEMS microphone.
The piezoelectric MEMS microphone includes only a vibration membrane. When the vibration membrane is deformed by an external sound pressure, an electrical signal is generated due to a piezoelectric effect. As a result, sound pressure is measured based on the electrical signal.
The capacitive MEMS microphone includes a fixing layer and a vibration membrane. When external sound pressure is applied to the vibration membrane, a capacitance value thereof is changed as an interval between the fixing layer and the vibration membrane is also changed.
In this case, the changed capacitance is outputted as a voltage signal, which corresponds to sensitivity, one of main performance indicators for the capacitive MEMS microphone.
To improve such sensitivity, reducing rigidity of the vibration membrane is desired.